There is an output breaker on the generator itself; check that. Some breakers don't look much or any different when they trip, so I would suggest flipping them off and on to reset even if they look OK.
If you don't have an automatic transfer switch, make sure the shore power cord is plugged into the socket for the generator which typically is located in the cord storage area. If you do have an automatic transfer switch, it may be misbehaving or broken. In any case, it's possible that there's a loose or broken connection between the generator and the electric panel, or a fault with the generator, though most RV generators would shut themselves down in the latter case.